PAL-Timing scheme for a bad scan line, no sprites:
+---------------------------------------------------------------+
| 1 2 3 4 5 6 |
|123456789012345678901234567890123456789012345678901234567890123|Cycles
+---------[------(--------------------------------------)---]---+Borders
|3-4-5-6-7-rrrrrgggggggggggggggggggggggggggggggggggggggg-N0-1-2-|Phi-1 VIC
| cccccccccccccccccccccccccccccccccccccccc |Phi-2 VIC
|xxxxxxxxxxxXXX========================================xxxxxxxxx|Phi-2 CPU
+---------------------------------------------------------------+
'-' = idle bus cycle (reads from the last byte of the video bank)
<num> = pointer fetch for sprite <num> ; g = graphics fetch
r = memory refresh cycle ; c = character pointer and/or color data fetch
N = extra '-' cycles for NTSC added here
x = processor executes instructions (BA high, AEC high)
X = bus request pending, bus still available (BA low, AEC high);
processor may execute write cycles, stops on the next read cycle.
'=' = bus unavailable (BA low, AEC low); processor is blocked because it
would like to read something.